At the present time, in the automobile field, as surfaces for electrical contact elements and plugs, for example, tin surfaces are predominantly used, i.e. hot-dipped substrate or substrate having a galvanically deposited tin layer in a range of thickness of a few micrometers. In this context, tin stands out by its ductility as well as very good electrical conductivity.
As base material or substrate for electrical plug connectors or plugs having a surface tin layer, alloys are used as a rule, that are copper-based, such as bronze, so that an intermediate layer develops by diffusion at the boundary between the tin layer and the substrate, which is made up of an intermetallic compound, such as a compound of the composition CuSn3, Cu5Sn6. This is harder than the tin layer that is located over it and is able to grow too, depending on the temperature.
Finally, it is known that one may apply a layer made of so-called “Thermotin” onto plugs and/or plug contacts, i.e. a layer based on intermetallic phases with tin that has been created by hot exposure. Because of their low hardness and their low resistance to wear, as is well known, tin alloys, when subjected to frequently repeated plugging or vehicle-caused or engine-caused vibrations, tend to fraying as well as to intensified oxidation (friction oxidation), which, in the case of a motor vehicle may lead to the failure of a component, especially a sensor, a control unit or another type of electrical component.
In known surfaces of plug connections that are based on tin, it is also of disadvantage that the insertion forces that come about due to the great tendency to adhesion and plastic deformability are frequently very great.